The present invention generally relates to CFAR signal processors. As is known, cell-averaging CFAR senses the environment in the vicinity of a test cell for the presence of a target and, based upon the sensed data, its environmental estimation controls a threshold level to make the false alarm probability constant. One difficulty, however, is that large extraneous reflectors, such as other targets and point clutter reflectors, may cause the threshold level to be raised to such a high level that the probability of target detection is seriously reduced.
A principal object of the present invention is therefore avoid the effect of extraneous targets by providing a CFAR processor capable of sensing their presence in one or more of the threshold control cells and of removing the targets from the computation which produces the threshold detection level.
A more specific object is to process the video from a radar sweep integrator in the manner and for the purpose outlined in the foregoing object.
There are a variety of techniques employed for CFAR processing. The ensuing detailed description focusses primarily upon the so-called simple cell-averaging processing. Other types which also will be briefly discussed include Logarithmic cell-averaging, Lognormal Interference processing and Weibull Interference. The following references provide supplementary data on these processing techniques:
1. H. M. Finn, R. S. Johnson, "Adaptive detection mode with threshold control as a function of spatially sampled clutter level estimates," RCA Review, Vol. 29, pp. 414-464, Sept. 1968.
2. V. G. Hansen, H. R. Ward, "Detection performance of the cell averaging log/CFAR receiver," IEEE Trans. Aerospace and Electronic Systems, Vol. AES-8, No. 5, pp. 648-654, Sept. 1972.
3. G. B. Goldstein, "False alarm regulation in log-normal and Wiebull clutter," IEEE Trans. Aerospace & Electronic Systems, Vol. AES-9, No. 1 Jan. 1973.
4 . V. G. Hansen, "Generalized constant false alarm rate processing and an application to the Wiebull distribution," 1972 IEEE Symp. Info. Theory, Asilomar, Calif., Jan. 1972.
In general, the present processor is suitable for use in any type of processing where surrounding resolution cells sense the environment to establish a detection threshold. Thus, the present system applies whether the cells are range cells, doppler shift cells, or both, or any combinations of coordinates, including azimuth and elevation.